The present invention relates generally to the detection of reagent levels in bodily and other fluids. In particular, the present invention relates to the use of visual color areas and bands on a colorimetric strip that allow easier and quicker inspection and analysis of test data.
To determine the presence or absence of, or the amount of, for example, albumin, glucose, leukocytes, occult blood, pH, specific gravity, or creatinine, in bodily or other fluids, a colorimetric strip is generally used by a laboratory technician to perform an analysis. A colorimetric strip contains one or more reagent areas at which a technician can apply sample fluid (by dipping the strip in the fluid or by other commonly known means) in order to compare the color of the reagent area after the fluid is applied to a reference color spectrum (often referred to as a reference color chart) for various levels of test results. The color spectrum is an array of expected colors appearing in the reagent area of the colorimetric strip and is generally located on a separate item such as on a bottle label.
A technician is forced to, in order to complete the analysis, perform the comparison between the color shade in the reagent area on the colorimetric strip to the shades on the color spectrum on the bottle label. This comparison is difficult because the color spectrum on the bottle label is exposed to the atmosphere and the color shades often fade, causing an inaccurate reading. Furthermore, lights and other colors and shades in the testing environment can effect the technician""s visual comparison between the colorimetric strip and an adjacent color spectrum on a bottle label and make the analysis and determination extremely burdensome. Finally, the technician may lose the bottle or the label, making the comparison virtually impossible.
The colorimetric strips of the prior art that are utilized in certain tests (e.g., for Albumin, Glucose, Leukocytes, and Occult Blood) attempt to determine the presence or absence of a particular compound being tested. Specifically, the technician must determine whether the reagent area on a colorimetric strip after application of the sample fluid is lighter or darker in shade than reference color shades for a negative and for a positive result. Generally, the two reference color shades used in presently used colorimetric strips consist of one reference area containing a color shade that yields a negative result and the other reference color area containing a color shade yielding a positive result. If the color obtained in the reagent area of the colorimetric strip is the same as or lighter than the negative spectrum color, a xe2x80x9cNegativexe2x80x9d result is obtained. If the reagent area, after application of the fluid, contains a color shade that is the same as or darker than the positive spectrum color on the colorimetric strip, the presence of the item being tested has been indicated and a xe2x80x9cPositivexe2x80x9d result is returned. However, if the reagent color appearing in previously manufactured colorimetric strips is darker than the reference area yielding a negative result and lighter than the reference area yielding a positive result, the user or technician must make a subjective determination whether the reagent area should produce a positive or negative result. Such subjective determinations are tedious, burdensome, and are likely to produce inconsistent results and improper analysis.
During other tests concerning colorimetric strips, the actual color obtained in the reagent area can produce a variety of results, instead of solely a comparison in color between the reagent area and the negative and positive reference color shades, as described above. In such tests, the color appearing in the reagent area is compared to the color spectrum specifically designed for that particular test (e.g., pH, Specific Gravity and Creatinine) in order to determine the appropriate color to match that in the color spectrum. A conclusion is reached by determining the color of the spectrum that most accurately matches the color on the reagent area. Each color in the spectrum is associated with a numerical value that corresponds to the value in the tested fluid of the item being tested. For example, on the reference color spectrum for the pH test, a resultant orange color corresponds to a pH value of approximately 5.0. Thus, if a reagent area on a colorimetric strip results in the same orange color existing in the pH reference color spectrum, the technician is able to conclude that the test fluid has a pH of 5.0.
When comparing the color obtained on the reagent area of the colorimetric strip to the different reference color spectrums, the specific color shade appearing in the reagent area does not often appear in the comparison color spectrum. The technician is often forced to choose between two adjacent colors in the spectrum to determine the most accurate match for the reagent area on the colorimetric strip. This choice becomes especially difficult when the color surfacing on the reagent pad appears to be midway between two color shades of the comparison color spectrum. In such a case, the user is equally as likely to decide that the reagent area color is nearer the lighter color shade as the darker color shade on the spectrum. An analysis that is equally likely to yield an incorrect result as a correct result can skew data and lead to improper analysis. Furthermore, some users interpret the reagent area color shades in order to obtain a result based on the significant number of hues that could be present (e.g., very light green, light green, green, strong green, deep green, very deep green), while other users simply interpret colorimetric strips based on a simple set of color shades (i.e. red, green, blue, etc.) that appear to exist in the reagent area without regard to the variety of different shades that exist within each color family. No standardized convention exists for making the comparison between the reagent area on the colorimetric strip and the colors in the reference spectrum. Actual practice varies between users, and this variance is problematic as the results of many of the tests technicians perform are considered based on their agreement to known visually determined reference results (i.e., the color spectrum referred to above). Accordingly, it is desirable to have a colorimetric strip that simplifies user analysis and increases the accuracy of sample interpretation and analysis.
The present invention improves the visual use of urine test strips and reagent pads by providing a single color from the reference color spectrum directly on the colorimetric strip and adjacent to the reagent area to allow easy comparison. After application of the fluid to be tested to a reagent area on the colorimetric strip, a technician is able to easily compare the color in the reagent area to the reference color area(s) and determine the presence or absence of, for example, glucose. Placing at least one reference color immediately next to the reagent area markedly improves technician""s accuracy in comparing and analyzing the reagent area against the reference color(s). One embodiment of the present invention also allows a technician to easily and quickly compare a reagent area color to more than one reference area to determine the actual numerical value of, for example, the pH in the tested fluid.